Effect of SnO2 and Rh modifications on CO-stripping kinetics and ethanol oxidation mechanism of Pt electrode

Tin dioxide-modified Pt electrodes with different coverages ( θ SnO 2 ) were prepared by potentiostatically depositing tin on a Pt electrode in 0.1 M H 2 SO 4 solutions containing various concentrations of SnCl 2 , followed by oxidizing in air. The θ SnO 2 was controlled by the SnCl 2 concentration. The CO-stripping voltammogram of the Pt/SnO 2 electrode with θ SnO 2 = 0.61 (Pt/SnO 2 (0.61)) exhibited two peaks, a prepeak due to the oxidation of adsorbed CO at Pt sites adjacent to SnO 2 and a main peak due to that at Pt sites far from SnO 2 . In the kinetic analysis of both peaks using CO-stripping voltammograms at various sweep rates, the rate-determining steps for the prepeak and main peak were the coupling of adsorbed CO on Pt with OH on SnO 2 surface by bifunctional effect and the dissociatively adsorption reaction of water to adsorbed OH on Pt, similar to the Pt electrode, respectively. In the linear sweep voltammograms of Pt/SnO 2 electrodes in a (0.1 M HClO 4 + 1 M ethanol) solution, the current for ethanol oxidation reaction (EOR) was the highest for θ SnO 2 = 0.61. The analysis of EOR products at different potentials for the Pt/SnO 2 (0.61) electrode by in situ infrared reflectance-absorption spectroscopy exhibited the Pt/SnO 2 (0.61) electrode facilitated acetic acid production. Moreover, rhodium was electrochemically deposited on the Pt sites adjacent to SnO 2 using the limited CO-stripping technique. The area-controlled Rh deposition did not change the rate-determining steps of both peaks, but it not only enhanced EOR activity, but also decreased acetic acid selectivity and increased CO 2 selectivity.